path: root/src/quick/items/context2d/qquickcanvasitem.cpp

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#include <private/qsgadaptationlayer_p.h>
#include "qquickcanvasitem_p.h"
#include <private/qquickitem_p.h>
#include <private/qquickcanvascontext_p.h>
#include <private/qquickcontext2d_p.h>
#include <qsgsimpletexturenode.h>
#include <QtQuick/private/qquickpixmapcache_p.h>

#include <qqmlinfo.h>
#include <private/qqmlengine_p.h>
#include <QtCore/QBuffer>

QT_BEGIN_NAMESPACE

class QQuickCanvasItemPrivate : public QQuickItemPrivate
{
public:
    QQuickCanvasItemPrivate();
    ~QQuickCanvasItemPrivate();
    QQuickCanvasContext* context;
    QSizeF canvasSize;
    QSize tileSize;
    QRectF canvasWindow;
    QRectF dirtyRect;
    uint hasCanvasSize :1;
    uint hasTileSize :1;
    uint hasCanvasWindow :1;
    uint available :1;
    uint contextInitialized :1;
    QQuickCanvasItem::RenderTarget renderTarget;
    QQuickCanvasItem::RenderStrategy renderStrategy;
    QString contextType;
    QHash<QUrl, QQuickPixmap*> images;
    QUrl baseUrl;
    QMap<int, v8::Persistent<v8::Function> > animationCallbacks;
};

QQuickCanvasItemPrivate::QQuickCanvasItemPrivate()
    : QQuickItemPrivate()
    , context(0)
    , canvasSize(1, 1)
    , tileSize(1, 1)
    , hasCanvasSize(false)
    , hasTileSize(false)
    , hasCanvasWindow(false)
    , available(false)
    , contextInitialized(false)
    , renderTarget(QQuickCanvasItem::FramebufferObject)
    , renderStrategy(QQuickCanvasItem::Cooperative)
{
}

QQuickCanvasItemPrivate::~QQuickCanvasItemPrivate()
{
    qDeleteAll(images);
}


/*!
    \qmlclass Canvas QQuickCanvasItem
    \inqmlmodule QtQuick 2
    \since QtQuick 2.0
    \brief The Canvas item provides a 2D canvas element which enables drawing via Javascript.
    \inherits Item
    \ingroup qml-basic-visual-elements

    The Canvas item allows drawing of straight and curved lines, simple and
    complex shapes, graphs, and referenced graphic images.  It can also add
    text, colors, shadows, gradients, and patterns, and do low level pixel
    operations. The Canvas output may be saved as an image file or serialized
    to a URL.

    To define a drawing area in the Canvas item set the \c width and \c height
    properties.  For example, the following code creates a Canvas item which
    has a drawing area with a height of 100 pixels and width of 200 pixels:
    \qml
    import QtQuick 2.0
    Canvas {
        id: mycanvas
        width: 100
        height: 200
    }
    \endqml

    Currently the Canvas item only supports the two-dimensional rendering context.

    \section1 Threaded Rendering and Render Target

    The Canvas item supports two render targets: \c Canvas.Image and
    \c Canvas.FramebufferObject.

    The \c Canvas.Image render target is a \a QImage object.  This render
    target supports background thread rendering, allowing complex or long
    running painting to be executed without blocking the UI.

    The Canvas.FramebufferObject render target utilizes OpenGL hardware
    acceleration rather than rendering into system memory, which in many cases
    results in faster rendering.

    The default render target is Canvas.Image and the default renderStrategy is
    Canvas.Threaded.

    \section1 Tiled Canvas
    The Canvas item supports tiled rendering by setting \l canvasSize, \l tileSize
    and \l canvasWindow properties.

    Tiling allows efficient display of a very large virtual canvas via a smaller
    canvas window. The actual memory consumption is in relation to the canvas
    window size.  The painting code can draw within the virtual canvas without
    handling coordinate system transformations.

    The tiles overlapping with the canvas window may be cached eliminating the
    need to redraw, which can lead to significantly improved performance in
    some situations.

    \section1 Pixel Operations
    All HTML5 2D context pixel operations are supported. In order to ensure
    improved pixel reading/writing performance the \a Canvas.Image render
    target should be chosen. The \a Canvas.FramebufferObject render target
    requires the pixel data to be exchanged between the system memory and the
    graphic card, which is significantly more expensive.  Rendering may also be
    synchronized with the V-sync signal (to avoid
    {en.wikipedia.org/wiki/Screen_tearing}{screen tearing}) which will further
    impact pixel operations with \c Canvas.FrambufferObject render target.

    \section1 Tips for Porting Existing HTML5 Canvas applications

    Although the Canvas item is provides a HTML5 like API, HTML5 canvas
    applications need to be modified to run in the Canvas item:
    \list
    \li Replace all DOM API calls with QML property bindings or Canvas item methods.
    \li Replace all HTML event handlers with the \a MouseArea item.
    \li Change setInterval/setTimeout function calls with the \a Timer item or
       the use of requestAnimationFrame.
    \li Place painting code into the \a QtQuick2::Canvas::onPaint handler and trigger
       painting by calling the \c markDirty or \c requestPaint methods.
    \li To draw images, load them by calling the Canvas's loadImage method and then request to paint
       them in the onImageLoaded handler.
    \endlist

    \sa QtQuick2::Context2D
*/

QQuickCanvasItem::QQuickCanvasItem(QQuickItem *parent)
    : QQuickItem(*(new QQuickCanvasItemPrivate), parent)
{
    setFlag(ItemHasContents);
}

QQuickCanvasItem::~QQuickCanvasItem()
{
    Q_D(QQuickCanvasItem);
    delete d->context;
}

/*!
    \qmlproperty size QtQuick2::Canvas::available

    Indicates when Canvas is able to provide a drawing context to operate on.
*/

bool QQuickCanvasItem::isAvailable() const
{
    return d_func()->available;
}

/*!
    \qmlproperty string QtQuick2::Canvas::contextType
    The type of drawing context to use.

    This property is set to the name of the active context type.

    If set explicitly the canvas will attempt to create a context of the
    named type after becoming available.

    The type name is the same as used in the getContext() call, for the 2d
    canvas the value will be "2d".

    \sa QtQuick2::Canvas::getContext QtQuick2::Canvas::available
*/

QString QQuickCanvasItem::contextType() const
{
    return d_func()->contextType;
}

void QQuickCanvasItem::setContextType(const QString &contextType)
{
    Q_D(QQuickCanvasItem);

    if (contextType.compare(d->contextType, Qt::CaseInsensitive) == 0)
        return;

    if (d->contextInitialized) {
        qmlInfo(this) << "Canvas already initialized with a different context type";
        return;
    }

    d->contextType = contextType;

    if (d->available)
        createContext(contextType);

    emit contextTypeChanged();
}

/*!
    \qmlproperty object QtQuick2::Canvas::context
    Holds the active drawing context.

    If the canvas is ready and there has been a successful call to getContext()
    or the contextType property has been set with a supported context type,
    this property will contain the current drawing context, otherwise null.
*/

QQmlV8Handle QQuickCanvasItem::context() const
{
    Q_D(const QQuickCanvasItem);
    if (d->contextInitialized)
        return QQmlV8Handle::fromHandle(d->context->v8value());

    return QQmlV8Handle::fromHandle(v8::Null());
}

/*!
    \qmlproperty size QtQuick2::Canvas::canvasSize
    Holds the logical canvas size that the context paints on.

    By default, the canvas size is the same size as the current canvas item
    size.

    By setting the canvasSize, tileSize and canvasWindow, the Canvas item can
    act as a large virtual canvas with many separately rendered tile rectangles
    Only those tiles within the current canvas window are painted by the Canvas
    render engine.

    \sa QtQuick2::Canvas::tileSize QtQuick2::Canvas::canvasWindow
*/
QSizeF QQuickCanvasItem::canvasSize() const
{
    Q_D(const QQuickCanvasItem);
    return d->canvasSize;
}

void QQuickCanvasItem::setCanvasSize(const QSizeF & size)
{
    Q_D(QQuickCanvasItem);
    if (d->canvasSize != size) {
        d->hasCanvasSize = true;
        d->canvasSize = size;
        emit canvasSizeChanged();

        if (d->contextInitialized)
            polish();
    }
}

/*!
    \qmlproperty size QtQuick2::Canvas::tileSize
    Holds the canvas rendering tile size.

    The Canvas item enters tiled mode by setting canvasSize, tileSize and the
    canvasWindow. This can improve rendering performance by rendering and
    caching tiles instead of rendering the whole canvas every time.

    Memory will be consumed only by those tiles within the current visible
    region.

    By default the tileSize is the same as the canvasSize.

    \sa QtQuick2::Canvas::canvaasSize QtQuick2::Canvas::canvasWindow
*/
QSize QQuickCanvasItem::tileSize() const
{
    Q_D(const QQuickCanvasItem);
    return d->tileSize;
}

void QQuickCanvasItem::setTileSize(const QSize & size)
{
    Q_D(QQuickCanvasItem);
    if (d->tileSize != size) {
        d->hasTileSize = true;
        d->tileSize = size;

        emit tileSizeChanged();

        if (d->contextInitialized)
            polish();
    }
}

/*!
    \qmlproperty rect QtQuick2::Canvas::canvasWindow
     Holds the current canvas visible window.

     By default the canvasWindow size is the same as the Canvas item size with
     the top-left point as (0, 0).

     If the canvasSize is different to the Canvas item size, the Canvas item
     can display different visible areas by changing the canvas windowSize
     and/or position.

    \sa QtQuick2::Canvas::canvasSize QtQuick2::Canvas::tileSize
*/
QRectF QQuickCanvasItem::canvasWindow() const
{
    Q_D(const QQuickCanvasItem);
    return d->canvasWindow;
}

void QQuickCanvasItem::setCanvasWindow(const QRectF& rect)
{
    Q_D(QQuickCanvasItem);
    if (d->canvasWindow != rect) {
        d->canvasWindow = rect;

        d->hasCanvasWindow = true;
        emit canvasWindowChanged();

        if (d->contextInitialized)
            polish();
    }
}

/*!
    \qmlproperty bool QtQuick2::Canvas::renderTarget
    Holds the current canvas render target.

    \list
    \li Canvas.Image  - render to an in memory image buffer.
    \li Canvas.FramebufferObject - render to an OpenGL frame buffer
    \endlist

    This hint is supplied along with renderStrategy to the graphics context to
    determine the method of rendering. A renderStrategy, renderTarget or a
    combination may not be supported by a graphics context, in which case the
    context will choose appropriate options and Canvas will signal the change
    to the properties.

    The default render target is \c Canvas.FramebufferObject.
*/
QQuickCanvasItem::RenderTarget QQuickCanvasItem::renderTarget() const
{
    Q_D(const QQuickCanvasItem);
    return d->renderTarget;
}

void QQuickCanvasItem::setRenderTarget(QQuickCanvasItem::RenderTarget target)
{
    Q_D(QQuickCanvasItem);
    if (d->renderTarget != target) {
        if (d->contextInitialized)         // target not changeable once context is active
            return;

        d->renderTarget = target;
        emit renderTargetChanged();
    }
}

/*!
    \qmlproperty bool QtQuick2::Canvas::renderStrategy
    Holds the current canvas rendering strategy.

    \list
    \li Canvas.Immediate - context will perform graphics commands immediately in the main UI thread.
    \li Canvas.Threaded - context will defer graphics commands to a private rendering thread.
    \li Canvas.Cooperative - context will defer graphics commands to the applications global render thread.
    \endlist

    This hint is supplied along with renderTarget to the graphics context to
    determine the method of rendering. A renderStrategy, renderTarget or a
    combination may not be supported by a graphics context, in which case the
    context will choose appropriate options and Canvas will signal the change
    to the properties.

    Configuration or runtime tests may cause the QML Scene Graph to render in
    the GUI thread.  Selecting \c Canvas.Cooperative, does not guarantee
    rendering will occur on a thread separate from the GUI thread.

    The default value is \c Canvas.Cooperative.

    \sa QtQuick2::Canvas::renderTarget
*/

QQuickCanvasItem::RenderStrategy QQuickCanvasItem::renderStrategy() const
{
    return d_func()->renderStrategy;
}

void QQuickCanvasItem::setRenderStrategy(QQuickCanvasItem::RenderStrategy strategy)
{
    Q_D(QQuickCanvasItem);
    if (d->renderStrategy != strategy) {
        if (d->contextInitialized)   // Render strategy not changeable once context is active
            return;

        d->renderStrategy = strategy;
        emit renderStrategyChanged();
    }
}

QQuickCanvasContext* QQuickCanvasItem::rawContext() const
{
    return d_func()->context;
}

void QQuickCanvasItem::sceneGraphInitialized()
{
    Q_D(QQuickCanvasItem);

    d->available = true;
    connect(this, SIGNAL(visibleChanged()), SLOT(checkAnimationCallbacks()));
    QMetaObject::invokeMethod(this, "availableChanged", Qt::QueuedConnection);

    if (!d->contextType.isNull())
        QMetaObject::invokeMethod(this, "delayedCreate", Qt::QueuedConnection);
    else if (receivers(SIGNAL(paint(QRect))) > 0)
        QMetaObject::invokeMethod(this, "requestPaint", Qt::QueuedConnection);
}

void QQuickCanvasItem::geometryChanged(const QRectF &newGeometry, const QRectF &oldGeometry)
{
    Q_D(QQuickCanvasItem);

    QQuickItem::geometryChanged(newGeometry, oldGeometry);

    QSizeF newSize = newGeometry.size();
    if (!d->hasCanvasSize && d->canvasSize != newSize) {
        d->canvasSize = newSize;
        emit canvasSizeChanged();
    }

    if (!d->hasTileSize && d->tileSize != newSize) {
        d->tileSize = newSize.toSize();
        emit tileSizeChanged();
    }

    const QRectF rect = QRectF(QPointF(0, 0), newSize);

    if (!d->hasCanvasWindow && d->canvasWindow != rect) {
        d->canvasWindow = rect;
        emit canvasWindowChanged();
    }

    if (d->available)
        requestPaint();
}

void QQuickCanvasItem::componentComplete()
{
    QQuickItem::componentComplete();

    Q_D(QQuickCanvasItem);
    d->baseUrl = qmlEngine(this)->contextForObject(this)->baseUrl();
}

void QQuickCanvasItem::itemChange(QQuickItem::ItemChange change, const QQuickItem::ItemChangeData &value)
{
    QQuickItem::itemChange(change, value);
    if (change != QQuickItem::ItemSceneChange)
        return;

    Q_D(QQuickCanvasItem);
    if (d->available)
        return;

    if (value.canvas == 0)
        return;

    d->canvas = value.canvas;
    if (d->canvas->openglContext() != 0) // available context == initialized
        sceneGraphInitialized();
    else
        connect(d->canvas, SIGNAL(sceneGraphInitialized()), SLOT(sceneGraphInitialized()));
}

void QQuickCanvasItem::updatePolish()
{
    QQuickItem::updatePolish();

    Q_D(QQuickCanvasItem);

    if (d->contextInitialized)
        d->context->prepare(d->canvasSize.toSize(), d->tileSize, d->canvasWindow.toRect(), d->dirtyRect.toRect(), d->smooth);

    if (d->animationCallbacks.size() > 0 && isVisible()) {
        QMap<int, v8::Persistent<v8::Function> > animationCallbacks = d->animationCallbacks;
        d->animationCallbacks.clear();

        foreach (int key, animationCallbacks.keys()) {
            v8::HandleScope handle_scope;
            v8::Handle<v8::Object> self = QQmlEnginePrivate::getV8Engine(qmlEngine(this))->newQObject(this).As<v8::Object>();
            v8::Handle<v8::Value> args[] = { v8::Uint32::New(QDateTime::currentDateTimeUtc().toTime_t()) };
            v8::Persistent<v8::Function> f = animationCallbacks.value(key);
            f->Call(self, 1, args);
            f.Dispose();
        }
    }
    else {
        if (d->dirtyRect.isValid()) {
            if (d->hasTileSize && d->hasCanvasWindow)
                emit paint(tiledRect(d->canvasWindow.intersected(d->dirtyRect.toAlignedRect()), d->tileSize));
            else
                emit paint(d->dirtyRect.toRect());
            d->dirtyRect = QRectF();
        }
    }

    if (d->contextInitialized) {
        if (d->renderStrategy == QQuickCanvasItem::Cooperative)
            update();
        else
            d->context->flush();
    }
}

QSGNode *QQuickCanvasItem::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *)
{
    Q_D(QQuickCanvasItem);

    if (!d->contextInitialized)
        return 0;

    class CanvasTextureNode : public QSGSimpleTextureNode
    {
    public:
        CanvasTextureNode() : QSGSimpleTextureNode() {}
        ~CanvasTextureNode() {delete texture();}
    };

    CanvasTextureNode *node = static_cast<CanvasTextureNode*>(oldNode);
    if (!node) {
        node = new CanvasTextureNode;
    }

    if (d->renderStrategy == QQuickCanvasItem::Cooperative)
        d->context->flush();

    node->setTexture(d->context->texture());
    node->setRect(QRectF(QPoint(0, 0), d->canvasWindow.size()));
    return node;
}

/*!
    \qmlmethod object QtQuick2::Canvas::getContext(string contextId, any... args)

    Returns a drawing context or null if no context available.

    The \a contextId parameter names the required context. The Canvas element
    will return a context that implements the required drawing mode. After the
    first call to getContext any subsequent call to getContext with the same
    contextId will return the same context object.

    If the context type is not supported or the canvas has previously been
    requested to provide a different and incompatible context type, null will
    be returned.

    Canvas only supports a 2d context.
*/

void QQuickCanvasItem::getContext(QQmlV8Function *args)
{
    Q_D(QQuickCanvasItem);

    if (args->Length() < 1 || !(*args)[0]->IsString()) {
        qmlInfo(this) << "getContext should be called with a string naming the required context type";
        args->returnValue(v8::Null());
        return;
    }

    if (!d->available) {
        qmlInfo(this) << "Unable to use getContext() at this time, please wait for available: true";
        args->returnValue(v8::Null());
        return;
    }

    QString contextId = QString::fromUtf16(*v8::String::Value((*args)[0]));

    if (d->context != 0) {
        if (d->context->contextNames().contains(contextId, Qt::CaseInsensitive)) {
            args->returnValue(d->context->v8value());
            return;
        }

        qmlInfo(this) << "Canvas already initialized with a different context type";
        args->returnValue(v8::Null());
        return;
    }

    if (createContext(contextId))
        args->returnValue(d->context->v8value());
    else
        args->returnValue(v8::Null());
}

/*!
    \qmlmethod long QtQuick2::Canvas::requestAnimationFrame(callback)

    This function schedules callback to be invoked before composing the QtQuick
    scene.
*/

void QQuickCanvasItem::requestAnimationFrame(QQmlV8Function *args)
{
    if (args->Length() < 1 || !(*args)[0]->IsFunction()) {
        qmlInfo(this) << "requestAnimationFrame should be called with an animation callback function";
        args->returnValue(v8::Null());
        return;
    }

    Q_D(QQuickCanvasItem);

    static int id = 0;

    d->animationCallbacks.insert(++id, v8::Persistent<v8::Function>::New(((*args)[0]).As<v8::Function>()));

    if (isVisible())
        polish();

    args->returnValue(v8::Int32::New(id));
}

/*!
    \qmlmethod void QtQuick2::Canvas::cancelRequestAnimationFrmae(long handle)

    This function will cancel the animation callback referenced by \a handle.
*/

void QQuickCanvasItem::cancelRequestAnimationFrame(QQmlV8Function *args)
{
    if (args->Length() < 1 || !(*args)[0]->IsInt32()) {
        qmlInfo(this) << "cancelRequestAnimationFrame should be called with an animation callback id";
        args->returnValue(v8::Null());
        return;
    }

    d_func()->animationCallbacks.remove((*args)[0]->Int32Value());
}


/*!
    \qmlmethod void QtQuick2::Canvas::requestPaint()

    Request the entire visible region be re-drawn.

    \sa QtQuick::Canvas::markDirty
*/

void QQuickCanvasItem::requestPaint()
{
    markDirty(d_func()->canvasWindow);
}

/*!
    \qmlmethod void QtQuick2::Canvas::markDirty(rect area)

    Mark the given \a area as dirty, so that when this area is visible the
    canvas renderer will redraw it. This will trigger the "onPaint" signal
    handler function.

    \sa QtQuick2::Canvas::paint QtQuick2::Canvas::requestPaint
  */

void QQuickCanvasItem::markDirty(const QRectF& rect)
{
    Q_D(QQuickCanvasItem);
    if (!d->available)
        return;

    d->dirtyRect |= rect;

    polish();
}

void QQuickCanvasItem::checkAnimationCallbacks()
{
    if (d_func()->animationCallbacks.size() > 0 && isVisible())
        polish();
}

/*!
  \qmlmethod bool QtQuick2::Canvas::save(string filename)

   Save the current canvas content into an image file \a filename.
   The saved image format is automatically decided by the \a filename's
   suffix.

   Note: calling this method will force painting the whole canvas, not just the
   current canvas visible window.

   \sa canvasWindow canvasSize toDataURL
  */
bool QQuickCanvasItem::save(const QString &filename) const
{
    Q_D(const QQuickCanvasItem);
    QUrl url = d->baseUrl.resolved(QUrl::fromLocalFile(filename));
    return toImage().save(url.toLocalFile());
}

QImage QQuickCanvasItem::loadedImage(const QUrl& url)
{
    Q_D(QQuickCanvasItem);
    QUrl fullPathUrl = d->baseUrl.resolved(url);
    if (!d->images.contains(fullPathUrl)) {
        loadImage(url);
    }
    QQuickPixmap* pix = d->images.value(fullPathUrl);
    if (pix->isLoading() || pix->isError()) {
        return QImage();
    }
    return pix->image();
}

/*!
  \qmlmethod void QtQuick2::Canvas::loadImage(url image)
    Loads the given \c image asynchronously.

    When the image is ready, onImageLoaded will be emitted.
    The loaded image can be unloaded by the \a QtQuick2::Canvas::unloadImage method.

    Note: Only loaded images can be painted on the Canvas item.
  \sa QtQuick2::Canvas::unloadImage QtQuick2::Canvas::imageLoaded QtQuick2::Canvas::isImageLoaded
  \sa QtQuick2::Context2D::createImageData QtQuick2::Context2D::drawImage
  */
void QQuickCanvasItem::loadImage(const QUrl& url)
{
    Q_D(QQuickCanvasItem);
    QUrl fullPathUrl = d->baseUrl.resolved(url);
    if (!d->images.contains(fullPathUrl)) {
        QQuickPixmap* pix = new QQuickPixmap();
        d->images.insert(fullPathUrl, pix);

        pix->load(qmlEngine(this)
                , fullPathUrl
                , QQuickPixmap::Cache | QQuickPixmap::Asynchronous);
        if (pix->isLoading())
            pix->connectFinished(this, SIGNAL(imageLoaded()));
    }
}
/*!
  \qmlmethod void QtQuick2::Canvas::unloadImage(url image)
  Unloads the \c image.

  Once an image is unloaded it cannot be painted by the canvas context
  unless it is loaded again.

  \sa QtQuick2::Canvas::loadImage QtQuick2::Canvas::imageLoaded QtQuick2::Canvas::isImageLoaded
  \sa QtQuick2::Context2D::createImageData QtQuick2::Context2D::drawImage
  */
void QQuickCanvasItem::unloadImage(const QUrl& url)
{
    Q_D(QQuickCanvasItem);
    QUrl removeThis = d->baseUrl.resolved(url);
    if (d->images.contains(removeThis)) {
        delete d->images.value(removeThis);
        d->images.remove(removeThis);
    }
}

/*!
  \qmlmethod void QtQuick2::Canvas::isImageError(url image)
  Returns true if the \a image failed to load.

  \sa QtQuick2::Canvas::loadImage
  */
bool QQuickCanvasItem::isImageError(const QUrl& url) const
{
    Q_D(const QQuickCanvasItem);
    QUrl fullPathUrl = d->baseUrl.resolved(url);
    return d->images.contains(fullPathUrl)
        && d->images.value(fullPathUrl)->isError();
}

/*!
  \qmlmethod void QtQuick2::Canvas::isImageLoading(url image)
  Returns true if the \a image is currently loading.

  \sa QtQuick2::Canvas::loadImage
  */
bool QQuickCanvasItem::isImageLoading(const QUrl& url) const
{
    Q_D(const QQuickCanvasItem);
    QUrl fullPathUrl = d->baseUrl.resolved(url);
    return d->images.contains(fullPathUrl)
        && d->images.value(fullPathUrl)->isLoading();
}
/*!
  \qmlmethod void QtQuick2::Canvas::isImageLoaded(url image)
  Returns true if the \a image is sucessfully loaded and ready to use.

  \sa QtQuick2::Canvas::loadImage
  */
bool QQuickCanvasItem::isImageLoaded(const QUrl& url) const
{
    Q_D(const QQuickCanvasItem);
    QUrl fullPathUrl = d->baseUrl.resolved(url);
    return d->images.contains(fullPathUrl)
        && d->images.value(fullPathUrl)->isReady();
}

QImage QQuickCanvasItem::toImage(const QRectF& rect) const
{
    Q_D(const QQuickCanvasItem);
    if (d->contextInitialized) {
        if (rect.isEmpty())
            return d->context->toImage(canvasWindow());
        else
            return d->context->toImage(rect);
    }

    return QImage();
}

/*!
  \qmlmethod string QtQuick2::Canvas::toDataURL(string mimeType)

   Returns a data URL for the image in the canvas.

   The default \a mimeType is "image/png".

   \sa QtQuick2::Canvas::save
  */
QString QQuickCanvasItem::toDataURL(const QString& mimeType) const
{
    QImage image = toImage();

    if (!image.isNull()) {
        QByteArray ba;
        QBuffer buffer(&ba);
        buffer.open(QIODevice::WriteOnly);
        QString mime = mimeType.toLower();
        QString type;
        if (mime == QLatin1Literal("image/png")) {
            type = QLatin1Literal("PNG");
        } else if (mime == QLatin1Literal("image/bmp"))
            type = QLatin1Literal("BMP");
        else if (mime == QLatin1Literal("image/jpeg"))
            type = QLatin1Literal("JPEG");
        else if (mime == QLatin1Literal("image/x-portable-pixmap"))
            type = QLatin1Literal("PPM");
        else if (mime == QLatin1Literal("image/tiff"))
            type = QLatin1Literal("TIFF");
        else if (mime == QLatin1Literal("image/xpm"))
            type = QLatin1Literal("XPM");
        else
            return QLatin1Literal("data:,");

        image.save(&buffer, type.toAscii());
        buffer.close();
        QString dataUrl = QLatin1Literal("data:%1;base64,%2");
        return dataUrl.arg(mime).arg(QLatin1String(ba.toBase64().constData()));
    }
    return QLatin1Literal("data:,");
}

void QQuickCanvasItem::delayedCreate()
{
    Q_D(QQuickCanvasItem);

    if (!d->contextInitialized && !d->contextType.isNull())
        createContext(d->contextType);

    requestPaint();
}

bool QQuickCanvasItem::createContext(const QString &contextType)
{
    Q_D(QQuickCanvasItem);

    if (contextType == QLatin1String("2d")) {
        if (d->contextType.compare(QLatin1String("2d"), Qt::CaseInsensitive) != 0)  {
            d->contextType = QLatin1String("2d");
            emit contextTypeChanged(); // XXX: can't be in setContextType()
        }
        initializeContext(new QQuickContext2D(this));
        return true;
    }

    return false;
}

void QQuickCanvasItem::initializeContext(QQuickCanvasContext *context, const QVariantMap &args)
{
    Q_D(QQuickCanvasItem);

    d->context = context;
    d->context->init(this, args);
    d->context->setV8Engine(QQmlEnginePrivate::getV8Engine(qmlEngine(this)));
    d->contextInitialized = true;
    connect(d->context, SIGNAL(textureChanged()), SLOT(update()));
    connect(d->context, SIGNAL(textureChanged()), SIGNAL(painted()));
    emit contextChanged();
}

QRect QQuickCanvasItem::tiledRect(const QRectF &window, const QSize &tileSize)
{
    if (window.isEmpty())
        return QRect();

    const int tw = tileSize.width();
    const int th = tileSize.height();
    const int h1 = window.left() / tw;
    const int v1 = window.top() / th;

    const int htiles = ((window.right() - h1 * tw) + tw - 1)/tw;
    const int vtiles = ((window.bottom() - v1 * th) + th - 1)/th;

    return QRect(h1 * tw, v1 * th, htiles * tw, vtiles * th);
}

/*!
    \qmlsignal QtQuick2::Canvas::onPaint(rect region)

    This handler is called to render the \a region. If a context is active it
    can be referenced from the context property.

    This signal can be triggered by QtQuick2::Canvas::markdirty,
    QtQuick2::Canvas::requestPaint or by changing the current canvas window.
*/

/*!
    \qmlsignal QtQuick2::Canvas::onPainted()

    This handler is called after all context painting commands are executed and
    the Canvas has been rendered.
*/

QT_END_NAMESPACE